BETA-BEAMS

1
BETA-BEAMS
b
Piero Zucchelli - CERN M. Mezzetto D.
Casper M. Lindroos U. Koester S. Hancock B.
Autin M. Benedikt H. Haseroth M. Grieser A.
Jansson S. Russenschuck F. Wenander

• 363 days after

Physics Letters B 532 (3-4) (2002) pp. 166-172
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GUIDELINES
A. Neutrino beams from a different perspective
B. The Beta-Beam Concept
C. Experimental Scenario
D. Beta-beams and neutrino physics
E. Feasible? Cost-effective? Competitive?
Current talk, previous talks, tables, sources
http//cern.ch/Piero.Zucchelli/files/betabeam. A
Website by this summer.
3
Focussing Properties
A
n are produced by weak decay of a parent
m,p,K,nucleus. We assume the decay to be
isotropic at rest and call E0 the rest frame
energy of the neutrino.
The focussing properties are given only by - the
divergence of the parent beam - the Lorentz
transformations between different frames PT pT
PLG ( p p ? cosq ) from which, on
average Q ?1/G (it depends ONLY on parent
speed!) E?GE0 and, in the forward
direction, E?2GE0 (same rest-frame spectrum shape
multiplied by 2G)
n
parent
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LBL Scope
A
maximum neutrino flux for a given Dm2?E/L?GE0/L.
The neutrino flux onto a far detector goes
like F?G2/L2 Therefore F?(Dm2)2/E02. At a
given parent intensity, low energy decays in the
CMS frame are the most efficient in achieving
the LBL requirement, and independently of the
G factor. But we want to observe neutrino
interactions N F ? s If we assume to be in
the regime where s ? E (gt300 MeV for nm) N ?
(Dm2)2 G/E0 And acceleration enters into the
game The Quality Factor of a
non-conventional neutrino beam is therefore
G/E0
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The BETA-BEAM
B
1. Produce a Radioactive Ion with a short
beta-decay lifetime 2. Accelerate the ion in a
conventional way (PS) to high energy 3. Store
the ion in a decay ring with straight
sections. 4. It will decay. ne (ne) will be
produced.
6He Beta- G150 E01.9 MeV QF79
- SINGLE flavour - Known spectrum - Known
intensity - Focussed - Low energy - Better Beam
of ne (ne)
Muons G500 E034 MeV QF15
18Ne Beta G250 E01.86 MeV QF135
The quality factor QFG/E0 is bigger than in a
conventional neutrino factory. In addition, ion
production and collection is easier. Then,
500000X more time to accelerate.
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Possible b- emitters (ne)
B
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Possible b emitters (ne)
B
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Anti-Neutrino Source
B
Consider 6He?6Li ne e-
E0?3.5078 MeV T/2 ? 0.8067 s
1. The ion is spinless, and therefore decays at
rest are isotropic.
2. It can be produced at high rates, I.e. 5E13
6He/s
DATA and theory ltEkinegt1.578 MeV ltEngt1.937
MeV RMS/ltEngt37
3. The neutrino spectrum is known on the basis
of the electron spectrum.
B.M. Rustand and S.L. Ruby, Phys.Rev. 97 (1955)
991 B.W. Ridley Nucl.Phys. 25 (1961) 483
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Neutrino Source
B
Possible neutrino emitter candidate18Ne The
same technology used in the production of 6He is
limited in the 18Ne case to 1012 ions/s. Despite
it is very reasonable to assume that a dedicated
RD will increase this figure, this intensity is
used as today reference. Issues MgO less
refractory, heat dissipation
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The Acceleration principle
B
ISOL Target and ECR
Linac
Cyclotron
Storage Ring
PS
SPS
Decay ring/Buncher
Bunch rotation is the crucial issue for
atmospheric background control!
Studies are made on EXISTING CERN machines. Why?
Much more detailed knowledge exists, the best way
to identify possible problems and limitations.
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Bunched?
B
The interactions time structure in the detector
is identical to the time structure of the parents
in the decay ring in a given position. The beta
decay position does not matter, since the
parents have the same speed of the neutrinos
The far detector duty cycle is bunch length /
ring length
A
B
Ion intensity
time
Interactions
time
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The Decay Ring
B
straight section relative length fixed to 2500 m
(SPS diameter). The ring is essentially flat
below ground (10 mrad).
100kW decay losses into the decay ring One bunch
of 10 ns length From the physics point of
view, the bigger the ring is, the better.
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A Neutrino Physics Scenario
C
It is reasonable to assume that - in the next
years - savings issues will dominate the scenario
in EU HEP. A. Imagine a neutrino detector that
could do Physics independently of the neutrino
factory. B. Imagine to build it, to run it, and
to explore non-accelerator physics. C. Imagine
that, as soon as the SPL will be ready (2015?),
you make a superbeam shooting muon neutrinos
onto it. If this will expand the physics reach,
and youre competitive with the other world
programs, youre ready to do it (known
technology). D. Imagine that you have PREPARRED
and STUDIED an option to shoot electron
neutrinos onto the same detector. If the next
neutrino physics will demand it, youre ready to
do it.
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A Dream?
C
A. the 600 Kton UNO detector. B. Supernovae,
Solar, Atmospheric, Proton Decay q12,m12,q23,m23.
C. Frejus site and SPL Super-Beam possibly q13
D. Frejus site and SPS Beta-Beam possibly q13
, possibly CP (2) and T
Is this physics program less wide than a
muon-based neutrino factory program? The
objectives are wider, the discovery potential is
smaller. But, for example, we will see that the
information on d, if within reach, is even more
comprehensive than a muon-based nufactory.
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SuperBeam Sinergy
C
The proton requirements of the Beta-Beam are
part of the ISOLDE_at_SPL (100uA for 1s every 2-5
s). The ISOLDE_at_SPL plans 100 uA protons
overall. The Superbeam uses 2mA from the SPL.
Therefore The BetaBeam affects the SuperBeam
intensity by 3 at most.
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Why Cherenkov?
C
The detector needs to be very massive, and
capable to distinguish electrons from
muons Same requirement of the SuperBeam! You
dont need the charge identification... ...Ther
efore you dont need a magnetic detector!
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The Far Detector Observables
D
The relative neutrino flux for a spinless
parents is ONLY function of g and L, not even of
the parent itself.
( as it is for 6He and 18Ne)
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The Far Detector Background
D
beam-related backgrounds due to Lithium/Fluorine
interactions at the end of the straight sections
GEANT3 simulation, 3E6 proton interactions onto
a Fe dump, tracking down to 10 MeV 100
mrad off-axis and 130 km distance. DIF and DAR
(K) contributions
lt10-4 background _at_ g150
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Cross Sections
D
antineutrinos interactions on Oxygen are
typically penalized by a factor 6.
However Free protons of H2O should also be
included
T.K Gaisser and J.S. OConnel, P.R.D34,3 (1986)
822.
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The Signal maximization...
D
The signal coming from appearance nm interactions
after oscillation _at_ 130 km and 440 kt-year
fiducial mass in the hypothesis
(q13p/2,m132.4E-3 eV2). The machine duty-cycle
is assumed to remain constant.
table
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and the interaction background...
D
NC interactions potentially produce D decays
(almost at rest) and the p is misidentified as a
muon. Asymmetries with Superbeams start to
appear (the e/p0 separation becomes
m/p) Kinematical cuts are possible, still
delicate and MC dependent. Another strategy
consists in having the pions below Cherenkov
threshold (see later).
Interaction Background
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...and the Atmospheric background
D
The atmospheric neutrino background has to be
reduced mainly by timing on the 6He bunches
(protons for the SuperBeam). The shortness of
the ion bunches is therefore mandatory (10 ns for
a SPS ring length). However, the directionality
of the antineutrinos can be used to further
suppress this background by a factor 4-6X
dependent on gamma.
Atmospheric Background
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Anue Summary Numbers
D
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The Nue case
D
Neon production Intensity is lower, HOWEVER 1.
18Ne has charge 10 and mass 18. 2. For the
previous reason, SPS can accelerate the ion up
to G250 (250 GeV/nucleon) WITH THE SAME MAGNETIC
FIELD used for 6He and G150. ltEngt0.93 GeV
!!! 3. For the same reasons explained for the
antineutrino case, the potential oscillation
signal improves despite the fact ltEgt/L7E-3
GeV/km
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Nue Summary Numbers
D
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The Super-Beta Beams (SPL-BB)
D
Beta-Beam nue 18,950 QE/Year _at_ 930 MeV _at_ 130 km

Beta-Beam anue 37,250 QE/Year _at_ 580 MeV _at_ 130 km
(Old) Super-Beam numu 9,800 QE/Year _at_ 260 MeV _at_
130 km
(Old) Super-Beam anumu 2050 QE/Year _at_ 230 MeV _at_
130 km
Obviously the SuperBeam lower energy is
better. Still, the oscillation probability of
the Beta-Beams are 37 (anue) and 15 (nue)
respectively. The SuperBeam has more beam-related
background, but is much simpler to do. Beta-beam
detector backgrounds to be studied.
ONE DETECTOR, ONE DISTANCE, 2X2 BEAMS!
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A CP or a T search?
D
CP Asymmetry
J. Sato, hep-ph 0006127
T Asymmetry
In the T search, ambiguities are resolved! The
tunability of the beta-beam allows additional
choice of the phase cot (Dm213 L / 4E)
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General Considerations
D
A. q13 is just the starting step for
superbeta-beams. B. CP violation at low energy
is almost exempt from matter effect, therefore
already particularly attractive (nue beta-beam,
anue beta-beam). C. Who else can do T violation
without magnetic field and electron charge
identification? (nue beta-beam, numu super-beam).
D. CPT test by anue beta-beam, numu super-beam
is the ultimate validation of the 3-family
mixing model and of the CP and T
measurements. E. If LSND is confirmed, 6 mixing
angles and 3 CP violation phases are waiting for
us! The smallness of the LSND mixing parameter
implies high purity beams, the missing unitarity
constraints will demand sources with different
flavours.
H. Minakata, H. Nunokawa hep-ph0009091.
CPT Asymmetry
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One simple Optimization
D
Background should not generate a Cherenkov
signal!
At the same time, it maximizes the overlap with
the CP-odd term (at CERN-Frejus distance)
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BetaBeam downgrading
D
11X Flux Drop!!!
g75, Flux Drop, Background Drop
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General Considerations
D
The neutrino factory golden-measurement is the CP
violation. Super-BeamBeta-Beam are competitive
in various ways, including T violation!
d 90 deg 99C.L. Curves
(M. Mezzetto, NNN02)
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Nu2002 comparison chart
E
F. Dydak
0.2-2 GeV
10-4
1
YesYes
Lets Fill the BB column!
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Comment on BB cost estimates
E
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My Last Words
E
1. the Beta-Beams are possible!
2. Unique, unprecedented high intensity high
purity ne/ne beams
3. Natural part of a program that starts with a
non-accelerator Water Cherenkov phase and a
SuperBeam phase. The program covers supernovae
detection, proton decay, atmospheric neutrinos,
solar neutrinos, q13 search, CP asymmetry, T
asymmetry, CPT asymmetry.
4. Scaled technology approach based on existing
accelerator technology
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Conclusions
Se son rose, fioriranno.
If they're roses, they will blossom
Si tiene barbas, San Antón, si no la Purísima
Concepción